1. Field of the Invention
The present invention relates generally to filtration housings for motors. More specifically, the present invention concerns modular filtration housings that hook on to the primary motor housing (i.e., housing protecting the stator and rotor) to protect the air intake openings from weather and other undesired debris. Each housing includes an inventive latching mechanism that enables the housing to be quickly and easily secured to the motor. Each housing complies with the National Electrical Manufacturers Association (“NEMA”) standards for a weather-protected Type II motor, therefore, the inventive housings enable a weather-protected Type I motor to be quickly and easily converted to a Type II motor. When assembled on the motor according to a preferred embodiment, the pair of filtration housings provide optimal and uniform cooling to the motor and enable a symmetrical, balanced motor that can be tested on a horizontal dynamometer with the housings attached.
2. Discussion of Prior Art
NEMA standard 1.25.8.1 defines a weather-protected Type I motor as a guarded motor with its ventilating passages so constructed as to minimize the entrance of rain, snow and air-borne particles to the electric parts. NEMA standard 1.25.8.2 defines a weather-protected Type II motor as a Type I motor additionally having its ventilating passages at both intake and discharge so arranged that high-velocity air and air-borne particles blown into the motor by storms or high winds can be discharged without entering the internal ventilating passages leading directly to the electric parts of the motor itself. NEMA standard 1.25.8.2 further requires the normal path of ventilating air which enters the electric parts to be so arranged by baffling or separate housings as to provide at least three abrupt changes in direction, none of which shall be less than ninety degrees. NEMA standard 1.25.8.2 additionally provides that either an area of low velocity not exceeding six-hundred feet per minute or an easy to clean (e.g., removable) filter shall be provided in the intake air path to minimize the possibility of moisture or dirt being carried into the electric parts of the motor.
Motors that satisfy the above-described NEMA standards for Type I motors are typically provided in most ratings ranging from small, fractional horsepower motors to very large horsepower motors (e.g., in excess of 10,000 HP). Type II motors are typically provided in ratings of three-hundred horsepower or higher. Both Type I and Type II motors can be used for a wide array of applications (e.g., horizontal or vertical-shaft pumps, indoor or outdoor generators, etc.). Type I motors do not require the additional filtration housings and thus are typically less expensive, lighter weight, and less part-intensive than the Type II motors. In this regard, depending on the ratings, these motors can weigh in excess of several tons. For example, a 1000 HP Type II motor can weigh as much as three tons with the filtration housing weighing several hundred pounds. It is preferred to use the less expensive Type I motors where possible, however, whether a Type I or Type II motor is appropriate for the specific application is largely governed by the operating environment for the application. Type I motors are typically used in fairly clean indoor applications or outdoors where there is sufficient protection from the elements (e.g., an overhead roof, etc.). Type II motors are typically utilized in relatively dirtier atmospheres where windborne dirt and/or moisture may be present. When the Type I motor is operating in a border line environment, it is desirable to utilize a Type II motor instead. Accordingly, it is desirable to have a motor that can be converted from a Type I to Type II motor.
Commercial motors that satisfy the above-described NEMA standards for either Type I or Type II motors are known in the art. These prior art motors typically include a stator and a rotor rotatably supported in a primary housing for driving a shaft coupled to the rotor. For a Type I motor, the intake openings formed in the housing are typically guarded by simple screens. For a Type II motor, the majority of the primary housing is typically guarded by a large shroud-like filtration housing that defines air flow to the intake openings. One example of these prior art motors are Emerson Electric Co.'s (the assignee of the present application) motors previously available under the designation Titan I.
While the Titan I motors were the most advanced motors in the art at the time, these prior art motors, like all other prior art motors, are problematic and subject to several undesirable limitations. For example, prior art motors are typically specially manufactured as either a Type I or a Type II motor, and cannot be readily converted to the other Type. In order to redesign a Titan I Type I motor to a Type II motor, for example, the shroud-like structure must be specially cut and welded around several motor fittings (e.g., the oil supply lines, the oil drain lines, etc.). If the shroud is not properly manufactured to fit, oil can undesirably drain into the motor without easy detection. This special manufacture is further hindered by the weight of the shroud (e.g., the shroud must be supported by a crane during fitting and manufacture) and is both part and labor intensive. For example, an entire day of man hours is required to specially manufacture and fit a Type II shroud on a Type I Titan I motor. The uniqueness of the prior art Type I and Type II motors undesirably necessitates stocking both Type I motors and Type II motors, resulting in undesirably high inventory costs. Additionally, the prior art Type II motors either undesirably draw hot exhausted air back into the intake openings or require an asymmetrical, unbalanced housing design that does not optimally and uniformly cool the motor (e.g., providing a “hot side” to the motor, etc.).